I know that Foo and Frobulator and so on have history in code examples, but I personally find examples with them require more careful reading than examples built on real concepts.

I teach for a living. Simple examples are fine for introducing a concept but students really grok it when they can see it in practice.

Something I've learned is that in general, people find it easier to follow concrete examples than abstract ones.

I agree with you that the article would have been improved if they'd used real-world examples, e.g. a ContactMethod type that has Address or PhoneNumber or something like that.